What I Have Learned



Activity 13: Complete me



Directions: Complete the paragraph by filling-in the blanks with the correct word from the box.



stromatolites human Beings

4.6 billion years ago Cenozoic

Earth ocean

zircon crystal Mesozoic Era

3.0 billion years ago

Homo erectus



About (1) , the earth was formed as the solar system came into existence with the other planets rotating around the sun. (2) is said to be geologically violent because of the continuous bombardment by meteorites and volcanic eruptions. With this condition, minerals were formed from the elements and compounds contained in the molten material. The oldest material found on earth is the (3) that is estimated to be 4.3 billion years old. Life on earth is believed to begin 3.5 billion years ago with single –celled prokaryotes, as discovered in sedimentary rock formations called (4) . As early as (5) , the first photosynthetic organism thrived the earth which is blue green algae called cyanobacteria. It was 2.0 billion years ago when the first eukaryotes appeared and the influx of multicellular organisms occurred 1.2 billion years ago. During the Paleozoic Era which lasted 542 to 251 MYA, the Cambrian and Ordovician Period has been known as the age of invertebrates when trilobites and cephalopods became dominant in the (6) . The (7) is the age of reptiles that has a span of 251 to 65.5 MYA divided into Triassic, Jurassic and Cretaneous Period. (8)

is the era of recent life and based on paleontological evidence (9) have evolved 250 thousand years ago. (10 are the only surviving species and one of the living evidences that life have existed on earth.​